Tension lock-up devices for printing plates



June 9, 1964 AUGUSTINE ETAL 3,136,247

TENSION LOCK-UP DEVICES FOR PRINTING PLATES Filed Oct. 4, 1961 2 Sheets-Sheet l imp,

INVENTOR. LEE AUGUSTINE AND HOWARD R. MASCHINOT,

2 flaw M ATTORNEYS J 1964 1.. AUGUSTINE ETAL 3,13e,247

TENSION LOCK-UP DEVICES FOR PRINTING PLATES Filed Oct. 4, 1961 2 Sheets-Sheet 2 INVENTOR. LEE AUGUSTINE AND HOWARD l2. MASCHINOT,

BYWVW ATTORNEYS United States Patent OfiFice 3,136,247 Patented June 9, 1964 The invention relates to means for fastening printing plates to the devices in printing presses which carry such plates; and in particular to the fastening of curved printing plates to cylindrical carriers. It has long been the practice to provide, in connection with grooved carriers having rack teeth in or near the bottoms of the grooves, clamping devices having bodies to enter the grooves, a swiveled jaw extending above the grooved surface, and means in the bodies and operable by a keylike device called a bit to move the clamping devices along the grooves. In this way the jaws of the clamping devices could be caused to engage edge portions of printing plates under compressive pressure so as to hold the plates to the carrier.

The same type of structure has been applied to hold curved printing plates to the surfaces of cylindrical carriers, wherein the grooves are disposed in a helical fashion. However, it has been realized that a compression lock-up is disadvantageous in the direction of the circumference of the cylinder, especially where the plates have a considerable circumferential extent. In other words, the application of compressive forces in the circumferential direction to the end portions of the printing plates has a tendency to cause the printing plates to bow in their central portions. This tendency is augmented by centrifugal force when the cylinders are rotated rapidly. Even though the bowing at the central portion of a long plate may be only a few thousandths of an inch, there will be a rapid flexing of the printing plates when they are brought repeatedly against the work sheet on the impression cylinder. This continual flexing, which is sometimes called breathing, subjects the material of the printing plates to fatigue so that platebreakage or cracking is not uncommon.

As a consequence, it has been suggested that the plates be fastened to the cylinders by engagement means which, in the circumferential direction, will exert tensional forces on the plates. This has been accomplished by the use of clamping devices operating in the helical grooves of the printing cylinders, which devices have jaws engaging in undercut grooves on the rear faces of the printing plates. The clamping means are frequently referred to as hooks, and this terminology will be used hereinafter in these specifications.

Difliculty has been encountered in providing hooks suitable for use in the helical grooves of plate cylinders. By reason of the pitch of the helical grooves, the hooks must have bodies of substantial length if they are to extend sufiiciently beyond the edges of the plates to permit operation by a suitable bit. The helical grooves in a cylinder are actually curved in two directions. Thus, a hook body of substantial length in order to fit a helical groove, must be curved in the longitudinal direction, and it must have a twist transverse the longitudinal direction. It would be quite difiicult and expensive to produce an elongated hook body by machining operations which were controlled to provide boththe curvature and the twist mentioned above. One of the objects of this invention is to provide a hook body which can be made i by ordinary machining operations and then given both invention.

bodies which were simply relieved toward their end portions sufiiciently to allow the bodies to be placed in the helical grooves of the plate cylinders. This, in and of itself, provided an intolerable loose fit of the hook body in the groove so that special devices had to be provided and operated to bring about a sliding contact of the hook body with the side edges of the grooves. It is an object of this invention to provide .a hook body of such character that upon insertion intoa helical groove the body will have a sufliciently snug sliding fit therein.

It will be understood that plate cylinders are made in different diameters for different uses. However, as the diameter of a plate cylinder becomes smaller-,the pitch of the helical grooves in its surface is also-diminished.

Through the practice of this invention it is possible tov printing plates. It has been found possible to limit the motion of the jaws in such a way that, while sufficient swiveling remains for the correct alignment of the jaw with the undercut face of the groove, the jaw will normally lie in a position only a few degrees removed from I parallelism with the groove in' the printing plate. It is an object of the invention to attain the convenience inherent in this feature.

Other objects of the invention have to do with the provision of tension hooks which are relatively .more simple and easier to construct, as well as-fsturdier and more dependable in'operation. i

There are several systems for plate lock-up employing grooves of slightly different configuration in plate supports. For the sake of an exemplary showing herein, the invention will be described and illustrated in connection with helically grooved plate cylinders wherein the grooves are of the well-known Warnock type; but it will be understood that the principles of the invention may hooks for use in be applied to the provision of tension the grooves employed in other systems. i

The objects of the invention which have been set forth above or which will be apparent to one reading these specifications are accomplished by that construction and arrangement of parts of which the aforesaid exemplary embodiment will now be described. 'Reference' is made to the accompanying drawings wherein: FIG. 1 is an elevational view ofa helically grooved FIG. 2 is an enlarged partial, plan view of a portion of the plate cylinder surface, showing a printing plate attached thereto by the tension hooks of this invention.

FIG. 3 is a partial plan-view on a still further enlarged scale showing a tension hookengaged in.a Warnock groove and holding a printing plate. I

FIG. 4 is a partiallongitudinal section of aprinting Ofi at right angles to a Warnock groove therein and .present ing an end view of a hook of this invention engaged in the groove. L

FIG. 6 is a side invention Y 7 FIG. 7 is a skeletoniiedview of an assembly of printing plate, plate cylinder and tension hook. I

FIG; 8 is a top plate showing the undercut groove in the rear face there- FIG. 5"is a partialsectional View of a cylinder taken elevation of the tension hook of this plan view. of the tension hook of this 7 FIG. 9 is a longitudinal sectional view taken along the line 9-9 of FIG. 8.

FIG. 10 is a perspective view of a spring element used in connection with the hook. 1

FIG. 11 is a perspective view of the under side of a spring retaining plate.

FIG. 12 is a perspective view of a tweezer-like device used for the removal of the tension hooks of this invention.

FIG. 1 shows a plate cylinder 1 having helical grooves 2 therein. Two printing plates, 3 and 4, are shown on the surface of the cylinder, these plates being curved to fit the peripheral surface thereof.

The shape of the groove in the Warnoclr construction will be best appreciated from the showing of FIGS. 5 and 7. The groove has an enlarged lower portion 5 which carries a double rack member 6, having a row of teeth on either side as shown at 7, and a central groovelike depression 8. The rack member is formed separately and is slid endwise into the enlarged groove portion 5 where it may be held to the cylinder 1 by screws (not shown). Lateral walls ill and ill of the groove slant upwardly and outwardly until at positions marked 12 and 13 they change plane and extend upwardly'in substantial parallelism. Above these portions there are inwardly extending shoulders 14 and 15, the purpose of which will hereinafter be described.

The hook itself has a body portion 16 of generally rectangular cross section (see FIGS. 6, 8, and 9). The width'of the body is such as to permit it to be inserted into a groove of the plate cylinder between the shoulders 14 and 15. On the bottom of the body there is a reduced extension 17ofa widthto lie within the central groove 3 of the rack member. This extension may advantageously be made somewhat smaller intermediate its end portions as shown at 18 in FIG. 8. The body 16 also has at its ends reduced portions 19 and 20 which are rounded at their bottoms to accept the bowed portions of spring members hereinafter described. The shape of'these end portions will be best seen in FIG. 7. The body also has a central recess 21 in its top portion to accept a spring retaining plate 22. A vertical bore 23 is formed in one end of the body to accept the swiveling post of a jaw member, and another similar bore 24 is formed near the other end of the body. A transverse bore 25 slightly in'te'rsectsthe bore .24, and these two bores contain the driving or propelling, mechanism which will later be described. There are some shallow grooves in the side portions of the body member indicated by thedotted lines 26 in FIG. 8. Q

There are also some small transverseholes through the body member to accept pins for purposes later outlined. A slot 27 is formed centrallyof the body extending upwardly from the bottom through a little more than half of its height. 7 The body member 'is configured as above described by machining, milling, boring, grinding, and equivalent opera tions. Thereafter, through the use of a press and dies, the body is given the two-directional curvature mentioned iently' formed as separate elements and mounted nonrotatively on a. shaft 36. The assembly will be held in the. bore 25 because of the engagement of the worm 28 in the necessarily hollowed central portion of the worm wheel. It will be appreciatedfrom FIGS. 6 and 7 that the teeth of the spur gears extend sufiiciently below the edge of the body at the sides of the body extension 17 so as to engage the teeth 7 of the rack member 6 in the bottom of the groove. Thus, the body may be propelled along the groove by rotating the bit 33.

A jaw 37 surmounts a post 38 which extends within the bore 23 of the body. The post has an external peripheral groove 39; and a pair of pins 40 and 41 are engaged with a press fit in a pair of transverse holes in the body so as to lie partly within the groove 39 to permit swiveling of the post. The jaw 37 is limited as to its motion for reasons set forth above; and this is most easily accomplished by providing an oversized bore 42 in the posted the properangularity to the jaw 37 and passing an undersized pin 43 through a transverse hole in the body and through the hole 42 of the post. The pin will have a press fit in the body, but it will permit a limited swiveling of the post and. jaw'while keeping the jaw Within-a few degrees of a desired angularity with the axis of the body.

The body is provided at either end with spring members such'as that illustrated in perspective inPlG. 10. Each spring member comprises a U-shaped yoke 44 which is adapted to pass around one of the extensions 19 or 2% on the ends of the hook body. Horizontal legs 45 and '46 are attached to the ends of the yoke. The

shorter ends of these legs (which extend beyond the ends of the body) are inwardly turned as at 7 and as. The other ends of the legs have inwardly offset portions .49 and 58. In order to hold these spring members in place on the body of the hook, use is made of the spring retaining plate 22 heretofore mentioned. This spring retaining plate, as shown in PEG. 11 (which shows the plate from the under side) is provided with opposed marginal ribs 51 and 5?, relieved at'their ends. There is a central above. The slot 27 facilitates both the longitudinal .bend- 'To provide a propelling mechanism, a worm 28 is bottom of the bore, and the other end is held in place by a hollow collar member 29. This member has an external peripheral groove and is held in place by pins 34 and 31 which, when-inserted in the previously mentioned small transverse holes in the bodymember. with'apress fit, will engage in the groove and hold-the collar member in' place.

placed in the bore 24.- It is supported on .one, end at the FIG. 12. This element comprises a hole 53 in the plate countersunk to receive the head oi a screw 54 by means of which the plate may be alfixed to the body. Legs 45 and es of the springm'embers lie partly within the grooves 26 of the body with the offset portions of the legs 49 and 5t) lyingbehind. the ribs 51 the body in the groove of the printing plate carrier by engaging beneath the inwardly extending groove shoulders 14 and 15; Thus, a hook will be held in its groove but will be movable therein under the influence of the propulsion meansabove described.

in removing the tension hooks of this invention, use is made of a'tweezer-like element such as is shown'in handlefilla, a pair ofarms 55 and S6, with semi-cylindrical, bottomed, hollow members 57 and 58 on the ends ofthe arms. If the hollow portions of this device are placed, in a groove of the plate carrier on either. end of a tension hook, and if 1 the arms 55 and 56 are urged together as by pressure or the fingers, the bent-over end portions 4'7 and 58 of the spring members-will be urged togeth r "by the end portions'of-the tweezers. Thus, the hool; will be disengaged from beneath'the inwardly extending shoulders Hand 15 of the groove, and the entire hook may be withdrawn radially from the groove.

In practice the printing plate will be provided with grooves or scarfs adjacent its edges which lie axially or substantially so of the plate cylinder. In FIGS. 4 and 7, where the plate 4 is shown in partial cross section, the transverse shape of the groove is indicated at 59, and it will be noted that the groove or scarf has an undercut face 60. The degree of undercutting need not be great (about departure from a plane normal to the plate surface being sufficient); and the shape of the groove is such that an undercut toe portion 61 of the jaw 37 will engage within the groove at the undercut groove face. As seen in FIG. 3, when this engagement is effected, and the hook member moved or tightened in a direction away from the plate as indicated by the arrow A, tensional stresses will be imposed on the plate in the direction of the arrow B. The hook is long enough so that the bit 33 may be engaged with the worm beyond the edge of the printing plate. In an actual lock-up, as illustrated in FIG. 2, the lateral edges of the plate will be engaged by the jaw members 62 of ordinary hooks. When the position of the plate has been adjusted longitudinally of the plate cylinder by means of these ordinary hooks, operation of the tension hooks of this invention will result in tensioning the plate circumferentially of the cylinder. Needless to say, the tension hooks of this invention permit adjustment of the position of the plate circumferentially of the cylinder. Breathing will be prevented along with the consequent cracking of the plates, and better printing may be done at a faster rate and a longer plate life.

Modifications may be made in the invention without departing from the spirit of it. Having described the invention in a certain exemplary embodiment, what is claimed as new and desired to be secured by Letters Patent is:

1. A tension hook comprising an elongated body substantially rectangular in cross section, a clamping jaw near one end of said body and propelling means near the other end of said body, said body having a longitudinal curvature, and a lateral twist, whereby it is enabled to follow a helical groove in a plate cylinder, an elongated narrow slot extending inwardly from the lower surface of said body substantially centrally thereof, whereby said longitudinal curvature and said lateral twist are facilitated.

2. The structure claimed in claim -1 wherein said clamping jaw is an elongated member extending above the top surface of said body and swiveled with respect thereto, and including means to limit the swiveling motion of said jaw in such a way as to keep the longitudinal axis of the jaw within a few degrees of a predetermined angular relationship to the longitudinal axis of said body.

3. The structure claimed in claim 2, wherein said body has reduced portions at each end, and including spring means at each end of said body, each of said spring means having a yoke portion passing around the reduced end of said body, and legs attached to said yoke portion and lying below but parallel to the upper surface of said body, means for fastening the ends of the-leg portions tosaid body near the central part thereof, said leg portions hav- 6 ing extensions beyond said yoke at their. opposite ends, which portions are engageable by a tool to contract said yoke.

4. The structure claimed in claim 3 wherein side portions of said body are grooved to accept the first mentioned leg portion.

5. The structure claimed in claim 4 wherein the central portion of the upper face of said body is recessed to V propelling means comprises a worm in a vertical bore in said body, hollow means for retaining said worm in said bore, said worm having means whereby it may be engaged and rotated through said hollow means by a bit, a Worm wheel located in a hollow bore in said body and engaging said worm, and spur gear means non-rotatably attached tov said worm wheel and having teeth exposed at the bottom of said body for engagement with the teeth of a rack in a helical groove of a plate cylinder.

7. The structure claimed in claim 6 intended for use in a cylinder groove wherein the rack member has teeth adjacent each lateral edge and a central longitudinal depression, and wherein the body of the tension hook has a downward extension substantially throughout its length and dimensioned to enter the depression in the rack.

8. A ten'sionhook comprising an elongated body substantially rectangular in cross section, a clamping jaw near one end of said body and propelling means near the other end of said body, said body having a longitudinal curvature and a lateral twist whereby it is enabled to follow a helical groove in a plate cylinder, an elongated narrow slot extending inwardly from the lower surface of said body substantially centrally thereof, whereby said longitudinal curvature and said lateral twist of said body is facilitated, and automatically acting laterally expanding means for locking said tension hook body in such a helical groove, said means being effective upon complete insertion of said body in the groove.

9. The structure claimed in claim 8 wherein said laterally expanding means have inturned projections beyond the ends' of said body, said projections being engageable by a tool insertable in the groove to contract said expanding means and lift the said body from the groove.

References Cited in the file of this patent UNITED STATES PATENTS 999,279 Warnock Aug. 1, 1911 1,247,574 Pitt Nov. 20, 1917 2,125,331 Brugmann Aug. 2, 1938 2,261,305 Stephenson Nov. 4, 1941 2,406,883 Luehrs Sept. 3, 1946 2,668,497 McWhorter Feb. 9, 1954 3,028,806 Luehrs Apr. 10, 1962 OTHER REFERENCES The Warnock Sectional Register Block, The Warnock-Towner Co., Chicago, January 25, 1905. 

1. A TENSION HOOK COMPRISING AN ELONGATED BODY SUBSTANTIALLY RECTANGULAR IN CROSS SECTION, A CLAMPING JAW NEAR ONE END OF SAID BODY AND PROPELLING MEANS NEAR THE OTHER END OF SAID BODY, SAID BODY HAVING A LONGITUDINAL CURVATURE, AND A LATERAL TWIST, WHEREBY IT IS ENABLED TO FOLLOW A HELICAL GROOVE IN A PLATE CYLINDER, AN ELONGATED NARROW SLOT EXTENDING INWARDLY FROM THE LOWER SURFACE OF SAID BODY SUBSTANTIALLY CENTRALLY THEREOF, WHEREBY SAID LONGITUDINAL CURVATURE AND SAID LATERAL TWIST ARE FACILITATED. 